Irritable aggression in rats, induced by chemical (drugs) and sensory (shock) means, will be investigated with reference to stimulus cues which may determine the initiation or maintenance of the attack response. Tactile senation from the vibrissae will be manipulated by local facial anesthesia as a method of defining its role in the stimulus complex required for the attack signal. Posturing and movement by a target animal will also be examined as potential elicitors of attack. Relevant attack cues will be assessed by a repeated exposure method to determine if continued presence or absence will affect their eliciting or inhibiting roles in aggression. The potential of prior experience to modify later aggression will be examined by manipulating social and sensory variables during the course of development.